Role of SMC1A overexpression as a predictor of poor prognosis in late stage colorectal cancer

Background: Structural maintenance of chromosomes 1A (SMC1A) is a member of the cohesion family of proteins that plays crucial roles in cell cycle control. Recent studies have concluded that SMC1A is involved in the pathogenesis of cancer. This study aims to evaluate the functional role of SMC1A in colorectal cancer (CRC) both in vitro and in vivo, and the underlying molecular mechanisms. Methods: We firstly investigated the expression levels of SMC1A in 427 CRC specimens. Antigen expression was determined by immunohistochemical analysis of SMC1A on tissue microarrays. Stable SMC1A knockdown CRC cell lines were employed. The effects of SMC1A depletion on cell growth in vitro were examined by MTT, colony formation and flow cytometry assays. Tumor forming was evaluated by nude mice model in vivo. To detect the activation of intracellular signaling, pathscan intracellular signaling array and western blotting were performed. Results: The expression of SMC1A was much stronger in CRC tumor tissues than in adenomas and normal colorectal tissues. High SMC1A expression, indicated as an independent poor prognostic predictor for patients with stage III and stage IV CRC, was correlated with overall survival (OS) (p = 0.008). Functional analysis indicated that SMC1A knockdown by small interfering RNA (siRNA) mediated the significant inhibition of cell proliferation; induced cell cycle arrest and apoptosis via the suppression of CDK4, PCNA and PARP; and blocked the activation of the Erk1/2 and Akt cascades in CRC cells. In addition, SMC1A depletion significantly decreased the growth of subcutaneously inoculated tumors in nude mice. Conclusions: These results suggest that SMC1A plays an essential role in the development of CRC and may be a predictive factor in patients with CRC. The inhibition of SMC1A may serve as a promising therapeutic strategy for human CRC.